I started taking this about 6 months ago and I know now that I will take it for the rest of my life. As someone who suffers from allergies to several things, as well as chronically waking up in the morning with fairly restricted nasal passages, I now take one of these capsules (600 mg) as soon as I get up and within about 15 minutes I can breathe much easier. A terrific immune system booster also -- as cysteine is the rate-limiting precursor to glutathione, the body's main fuel for the I.S.
The label doesn't say this, but you should also take vitamin C at the same time -- not only for synergistic effect, but to prevent any possibility of kidney stones from long term use. I'd recommend 500 mg with each capsule taken. Like all amino acids, take on an empty stomach with water (ie. 30 minutes before a meal or 2 hours after). I'd also suggest methionine for those who experience high histamine levels.

This specific product has helped a great deal with the lung issues I have as well as having a positive effect on my Liver. I have Stage 4 Scerosis & Hep 'C', my Liver just wasn't producing all the protiens it is supposed to & after prolonged use (3-4 months)my Liver has started to produce these protiens, and Enzymes it is supposed to now. Thank you for making your product readily available at the LOW PRICES you charge!! Being on Ontario Dissability, my budget is stretched thin ast is, and every $ saved adds up.
Sincerely;
Satisfied Customer!

I take this for HIV, 3 capsules per day. This adds up to 75 mcg selenium.
When taking this in combination with NOW's own Adam men's multi-vitamin, which contains the recommended 200 mcg selenium, one gets 275 mcg selenium. This is excessive.
I had my blood selenium level checked, and it was elevated. I chose to continue the Adam multi but stop this NOW NAC . I switched to the Jarrow NAC which doesn't have selenium.